It is known to use an ion beam to dope silicon wafers with a controlled concentration of an impurity to produce a semi-conductor material. Ion implanters used for silicon wafer treatment typically include an ion source and beam forming structure which causes ions emitted from the source to form an ion beam that follows a travel path to an ion implantation chamber. Within the ion implantation chamber silicon wafers are impacted by the ion beam.
In certain classes of ion implanters, these silicon wafers remain stationary and the ion beam is scanned across the wafer surface. In an alternate design, the wafers are caused to move through the ion beam. These latter systems include ion beams having a relatively large diameter, often as large as the diameter of the wafer that the ion beam impacts. A wafer support rotates wafers arranged in a circular array through the ion beam at controlled rates until proper dopant levels are reached.
Ion beam intensity is a measure of the number of particles per unit time at a given location of the ion beam cross section. The ion beam emittance is a measure of the angular spread of the beam at that location.
It is desirable to know the ion beam intensity and ion beam emittance across the extent of the ion beam. If doping problems occur, the intensity and emittance profile of the beam can be used for diagnosing those problems. Additionally, this information is useful when tuning the ion beam to assure consistency between successive wafer doping cycles.
It is desirable that ion beam profile information be readily available on an essentially "real time" basis so that technicians monitoring ion implanter performance can make adjustments based upon the ion beam profile. Rapid updating of beam profile information allows those adjustments to be made and the effect the adjustments have on beam profile studied and re-evaluated.